Concept:A colloid is a mixture in which fine particles of one substance are evenly dispersed throughout another substance, and the particles do not settle out on standing.
Explanation:Colloids have particle sizes between true solutions and suspensions.
In milk, tiny fat globules are dispersed throughout water, and they remain suspended rather than settling.
This makes milk an example of a colloid, specifically an emulsion of liquid in liquid.
Orange juice contains larger pulp particles that can settle, so it is closer to a suspension.
Saltwater and sugar dissolved in water form true solutions, where the solute particles dissolve completely into ions or molecules.
Only milk fits the definition of a colloid among the given options.
Answer:A. Milk